1. Field of the Invention
The present invention relates to a valve assembly suitable for use in a pressure system involving a pressure actuator, for example, an energy conversion engine, e.g. an internal combustion engine or a heat engine, e.g. a diesel engine, a Sterling cycle engine, a Miller cycle engine, and an Otto cycle engine. More particularly, the present invention relates to a sliding valve assembly for use in a pressure system and having an improved sealing system configured to reduce friction, heat and wear on the valve and body related sealing components.
2. Description of the Prior Art
Most modern internal combustion engines utilize a four stroke operating sequence known as the Otto cycle. The Otto cycle comprises an intake stroke, in which an intake valve opens and a mixture of air and fuel is directed into the cylinder of the engine. A compression stroke then occurs in which the piston compresses the mixture of fuel and air to increase the pressure in the cylinder. A spark provided by a spark plug ignites the mixture just before the piston reaches the top of the cylinder, causing the piston to be forced down in the cylinder in the power stroke. An exhaust valve then opens in the exhaust stroke, in which burned gases are forced out of the cylinder. The four strokes are repeated continuously during operation of the engine.
Internal combustion engines operating on the Otto cycle principal generally utilize spring-loaded poppet valves that selectively open and close the intake and exhaust ports during each cycle. In most engines, a crankshaft is coupled to a timing belt or chain, which in turn is coupled to a camshaft that rotates to open the intake and exhaust valves during the intake and exhaust strokes, respectively. A spring associated with each valve closes the valve during the other cycles.
There are several drawbacks associated with the use of such spring-loaded poppet valves. One drawback is that the valves protrude into the cylinder during each cycle, and there is an inherent risk that the piston may contact an open valve at a high force and cause substantial engine damage. Additionally, valve timing events may be limited due to the protrusion of the valve head into the cylinder.
Another disadvantage with the use of poppet valves in conventional internal combustion engines is that a relatively stiff spring is used to close the valves. Therefore, a relatively strong force is required to overcome the resistive force of the spring to open each valve during each cycle, reducing the efficiency of the engine. Moreover, due to the stiff resistive force provided by the springs, valve timing events may be limited. For example, there generally is a short time period during which both the intake valve and the exhaust valve are open when conventional poppet valves and stiff springs are employed. During this overlap period, unburned hydrocarbon molecules may remain in the combustion chamber for a subsequent cycle, thereby adversely affecting dynamic compression and reducing engine efficiency.
Yet a further disadvantage associated with the use of conventional poppet valves is that energy is lost as a result of an obstruction of the orifice, i.e., because a portion of a poppet valve protrudes through the orifice and into the cylinder. Moreover, flow into the cylinder through the intake port is disrupted when it contacts the head of the poppet valve, i.e., the portion of the valve that seals the orifice in the closed state. The intake valve head may cause turbulence and dead air space within the cylinder, which in turn reduces the efficiency of the engine. Furthermore, when the head of the exhaust valve protrudes into the cylinder during the exhaust stroke, burned gases may not efficiently flow out of the cylinder, which further reduces combustion capabilities.
Various sliding valve designs, which may be used in conjunction with internal combustion engines, have been developed to overcome several of the drawbacks associated with conventional poppet valves. One primary advantage of a sliding valve assembly is the capability to have a substantially unobstructed flow path. Specifically, because a conventional poppet valve is not employed, and therefore does not obstruct the flow path through an intake or exhaust port, a sliding valve has the potential to significantly increase airflow capability into a cylinder. Moreover, since the stiff springs used in conjunction with conventional poppet valves may be omitted, sliding valve assemblies may achieve reduced mechanical loads.
Some sliding valve assemblies have rotating discs, cylinders, sleeves and other spheroidal rotating mechanisms. Such previously known sliding valves may be timed such that their apertures overlap with the cylinder during the intake and exhaust strokes. However, due to their continuous seal contact, these known sliding valves may experience high temperatures and extreme friction, resulting in high rates of wear imposed on the valve and any related sealing mechanisms.
Moreover, such sliding valve assemblies generally have fixed aperture sizes, i.e., the size of the aperture in registration with the cylinder may not be varied as the valve is translated or displaced i.e. moved back and forth in a plane as opposed to rotation. Accordingly, the fuel consumption and emissions may be increased by providing a relatively large port aperture, resulting in low gas velocities, which adversely affect engine performance at low engine speeds, particularly during idling conditions.
Examples of sliding valve assemblies are disclosed in U.S. Pat. Nos. 1,722,873; 1,922,678; 2,074,487; and 5,694,890.
Another drawback associated with some of the sliding valve systems of the prior art is the complexity of the sealing system employing a significant number of seals. It would be desirable to provide an effective sealing system for a sliding valve system that employs significantly fewer components.
There is a need therefore to provide a sliding valve assembly that is configured to be easily incorporated into a pressure system, for example, energy conversion engines, e.g. internal combustion engines.
There is a still further need to provide a sliding valve assembly that is configured to reduce friction, heat and wear on the valve body and related sealing components.
There is yet a further need to provide a sliding valve assembly having an improved sealing system configured to effectively seal the valve and/or the combustion chambers of the piston cylinder assemblies associated with energy conversion engines or having an improved sealing system configured to effectively seal the valve and/or the pressure chambers associated with pressure systems.